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IC inspection and failure analysis using single-photon detection
S. Frohmann, E. Dietz, H.-W. Hübers
German Aerospace Center (DLR)
Institute of Optical Sensor Systems
Rutherfordstr. 2, 12489 Berlin, Germany
19 August 2020, Berlin
Outline
• IC Inspector
• IC Preparation
• Mode of Operations
NIR Microscopy
Optical Beam Induced Current Microscopy (OBIC)
Laser Fault Injection Analysis (LFI)
Thermal Laser Stimulation Analysis (TLS)
Photon emission Analysis (PEA)
• Pico Second Imaging Analysis (PICA)
• Conclusion
Compact Near Infrared Microscope
for IC and Security IC Inspection
IC Inspector
IC Inspector - Summary
• 5 Operation Modes
• 4 optical in- and output ports
• Highly modular and flexible
• Compact size
• Dual laser module (e.g. 980nm)
• Fast laser scanning (galvos)
• Diffraction limited performance
• High positioning precision (<100nm)
• High timing precision (<10ps)
Rugged and easy to use (e.g. no cleanroom environment, no sophisticated vibration isolation,
no liquid nitrogen cooling, automated measurements, and autofocus).
Altera Cyclone IV FPGA, 60nm Substrate thickness 10 µm
Chip preparation – Back-side
Package openend down to the
lead frame by grinding Lead frame further partly removed Thinned and polished die
Operation Modes
1. NIR Microscopy
2. Optical Beam Induced Current Microscopy
3. Laser Fault Injection Analysis
4. Thermal Laser Stimulation Analysis
5. Spatial and Temporal Photon Emission Analysis
NIR Microscopy
Dark field reflected light microscopy with NIR light
NIR Microscopy – Back-side Image Through Silicon Substrate
Look-up tables of 2 adjacent LEs
∼ 4.5 x 4.5mm
Altera Cyclone IV FPGA (60nm)
∼ 1 x 1 mm ∼ 190 x 190 µm
∼ 50 x 30 µm
Optical Beam Induced Current Micrcoscopy
The standard method for failure analysis to locate buried diffusion
regions, damaged junctions and gate oxide shorts
Optical Beam Induced Current – Principle
• Laser photon energy >
semiconductor band gap energy
• Images are formed by a locally
induced photocurrent
3.522 mm
3.2
71
mm
• OBIC Images are showing the electronic structure and defects
• Photocurrent from pn-junctions of transistors or diodes that are connected to output pins used
• Bias voltage can enhance image contrast
Optical Beam Induced Current – Example
Laser Fault Injection Analysis
Manipulation of code execution by altering the logical state of
single transistors or logical elements
Laser Fault Injection – Principle
• Laser photon energy >
semiconductor band gap energy
• Free charges causing a short
current that can alter the state of a
transistor or a logical group
Example: SRAM Manipulation in Microchip ATXMega 16A4
• A standard SRAM-cell has three pn-
junctions/transistors where its value can be
set and three where it can be reset
• Individual SRAM-cells can be precisely
addressed to alter the stored bit value
Example: SRAM Manipulation in Microchip ATXMega 16A4
Each transistor of the
6T-Cell is resolvable
Thermal Laser Stimulation
Thermally induced leakage current for
side-channel analysis
Thermal Laser Stimulation – Principle
• Laser photon energy < semiconductor
band gap energy
• TLS scans induce an additional
leakage current in switched-off
transistors
TLS Example – Direct SRAM Data Read Out
TLS-image of a SRAM-Block in ATXMega 16A4
• TLS map reveals the state of
the transistors
• E.g. memory cell have a
characteristic TLS scan
pattern that can be used to
read out the memory content
Photon Emission Analysis
Failure localization and side-channel analysis with
spatial and temporal techniques
Photon Emission Analysis – Field Effect Transistors, HCL
nMOS pMOS Hot carrier luminescence (HCL)
• Occurs when transistors operate in saturation mode and charge carriers flow through the conduction channel.
• The electrical field attains its maximum near the edge of the drain where some carriers gain enough energy to emit photons by direct and indirect transitions.
• The spectrum of HCL is given by the energy distribution of the carriers and hence ranges from the visible to the infrared.
• The photon emission probability depends on the supply voltage and is about 10−4 to 10−6 photons per electron.
off
on
Photon Emission Analysis
NIR Microscope CCD Image SPAD Signal
Pico Second Imaging Analysis
1. Microscope NIR overview image
2. Photon emission overview image -> Region of interest (ROI)
3. Temporal photon emission measurement of single ROIs
4. Correlation & computation of emission time tags Overlayed NIR microscope and photon emission image (red).
ROI
TDC bin width: 81ps.
Pico Second Imaging Analysis – Temporal Super Resolution
Time (ns)
Pho
ton
s (
cou
nts
)
Total system jitter for detecting a single HCL photon
Pico Second Imaging Analysis – Example
Screenshots from a PICA video
showing the signal propagation
through an inverter chain
consisting of 10 elements in an
Altera Max V CPLD.
The video was created from the
temporal data from the SPAD and
the spatial data from the CCD.
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Summary
• Semi-invasive optical signal tracking in fully operational ICs on the gate or
transistor level possible
• High timing precision of < 10 ps for optical analysis like PEA
• 5 different methods can be used for analyzes without having to make
additional modifications and adjustments to the system:
NIR Microscopy
OBIC
LFI
TLS
PEA
• Diffraction limited performance
• Modular design allows adaptation to new ICs and analysis methods with little
effort
Contacts
Sven Frohmann
Enrico Dietz
Heinz-Wilhelm Hübers
German Aerospace Center (DLR)
Institute of Optical Sensor Systems
Rutherfordstr. 2, 12489 Berlin, Germany
